1. Field
The present disclosure relates to a low-dielectric-constant thin film prepared to have high surface modulus and low dielectric properties and a method for preparing the same. More particularly, the disclosure relates to a low-dielectric-constant thin film having high strength and low dielectric properties as well as good thermal stability prepared by adding a multireactive cyclic silsesquioxane material when preparing a siloxane-based polymer matrix, and a method for preparing the same.
2. Description of the Related Art
As semiconductors are more and more integrated, decrease in signal transfer rate caused by increased RC delay in the wirings is becoming a serious problem. Thus, it is a major concern to reduce capacitance of interlayer dielectric thin films.
In this regard, U.S. Pat. Nos. 3,615,272, 4,399,266, 4,756,977 and 4,999,397 disclose polysilsesquioxane dielectric films (dielectric constant=about 2.5 to 3.1) that can be produced by the spin-on deposition (SOD) method instead of SiO2 dielectric films (dielectric constant=4.0) requiring chemical vapor deposition.
Also, hydrogen silsesquioxane and various preparation processes thereof are known in the art. For example, U.S. Pat. Nos. and 3,615,272 and 5,010,159 silicone resin compositions produced by hydrolysis and condensation using acid or base. U.S. Pat. No. 6,000,339 discloses a process for producing a silica-based material enabling thick layer formation and having improved oxygen plasma resistance and other physical properties. U.S. Pat. No. 5,853,808 discloses siloxane- and silsesquioxane-based polymers prepared from an organosilane compound having a reactive group substituted at the β-position in order to obtain an SiO2-rich thin film and a coating composition using the same.
Further, European Patent No. 0997497 A1 discloses compositions obtained by hydrolysis and condensation of various alkoxysilane compounds, including monoalkoxysilanes, dialkoxysilanes, trialkoxysilanes, tetraalkoxysilanes and trialkoxysilane dimers and mixtures thereof, and dielectric films produced using the same.
However, the dielectric thin films produced using the siloxane-based polymers prepared according to known methods do not provide a sufficiently low dielectric constant (2.7 or lower). In case a sufficiently low dielectric constant is provided, mechanical property is not good (film modulus≦3 GPa) and the content of organic carbon in the dielectric film is high. Although the polymers prepared from silicon compounds having Q structure such as tetramethoxysilane (TMOS) have good mechanical property, they have too high an SiO2 content. Thus, the dielectric constant tends to be very high because of high hygroscopy, which makes them inapplicable to low-dielectric-constant thin films (especially, low-dielectric-constant thin films prepared by the SOD process).
In addition, siloxane-based polymers having good compatibility with pore-forming materials, which are used together to provide a lower dielectric constant, are required recently.
Accordingly, a material for forming a low-dielectric-constant thin film that can be produced by the SOD process which has a low dielectric constant, superior tensile strength and other mechanical properties and excellent compatibility with pore-forming materials, is needed in the related art.